Which Epoxy Resin to Use?

“Which epoxy resin should I use?”  An excellent question, and one we get asked all the time.  So, let’s dive into the resin options in our 2:1 Non-Blushing system.  We will explain the differences between our LV or Low Viscosity resin and its counterpart FLAG resin so you know which one you want to use for your next project.

2:1 Non-Blushing System

First things first.  LV Resin and FLAG Resin are used exclusively in the MAS 2:1 Non-Blushing System.  It includes, LV Resin, FLAG Resin and three non-blushing hardeners, Slow, Medium and Fast.  The mix ratio is 2 parts resin to 1 part hardener by volume, which makes these easy to mix in any shop.  Both resins result in a clear, non-blushing, low-odor epoxy laminating system that can be used in a wide range of applications.  This includes, but is not limited to, laminating, clear coating and bonding.  You can add fillers like colloidal silica, cell-o-fill, wood flour and phenolic micro-balloons to make compounds for bonding, filleting, fairing or filling.

Low Viscosity Epoxy Resin

As you can see the two resins are very similar, with the main difference being that LV Resin is, you guessed it, lower in viscosity than FLAG Resin.  But, what does low viscosity even mean?  The viscosity of the resin is the thickness of the liquid and is typically measured in units called centipoise (cP).  The viscosity spectrum goes from low viscosity, something like water (1 cP), to high viscosity, something more like molasses (10,000 cP).  LV Resin has a viscosity similar to honey (1,000 cP).  Moral of the story, LV Resin is thinner than FLAG Resin.

FLAG Epoxy Resin

FLAG Resin is an acronym for, Filling, Laminating And Gluing, and as you might have assumed, these are the recommended uses for this product.  It is what we call a “medium viscosity” epoxy resin.  On the viscosity scale mentioned earlier between water and molasses, FLAG is somewhere in the middle.  The best way we can describe it is close to Maple Syrup (2,300 cP). Think Aunt Jemima before you put it in the microwave.

When do I use FLAG and when do I use LV?

Let’s go through some scenarios that would warrant the use of these two resins.

Laminating

  •  LV Resin

Why?  LV Resin is lower in viscosity and has excellent saturation into fiberglass and other cloths.  If you’re looking for a utilitarian product you can also use FLAG Resin for laminating, it will work into fiberglass cloth a little more slowly than LV Resin.

Gluing & Bonding

  • FLAG Resin (with or without fillers)

Why? The medium viscosity of FLAG Resin holds a thick bond line and can also be combined with a variety of fillers for improved gap filling and sag resistance on inclined surfaces.  FLAG Resin with MAS Colloidal Silica creates an excellent thickened high strength adhesive.

Filleting, Fairing & Filling

  • FLAG Resin (with fillers)

Why?  Similar to the explanation on gluing, FLAG should be used because of its higher viscosity.  You can easily add  different fillers to mixed resin and hardener to create filleting and fairing compounds or filling pastes.  FLAG Resin with MAS Wood Flour makes a perfect filleting material for stitch and glue construction.

Clear Coating

  • FLAG Resin

Why?  Even though both resins are clear, we often recommend FLAG Resin.  This is because FLAG’s medium viscosity helps to coat thicker with just fewer coats resulting in a smooth glassy finish.We hope this sheds some light on why we offer two different epoxy resins.  Both can be used for laminating and work with our Slow, Medium and Fast Hardeners, but have their own specialties.  The best part is they are both easy to use at 2:1 by volume and non-blushing.  Let us know if you have any questions and good luck with your projects!

11 comments

  1. Hi Mike here doing a project on my bathroom floor -a border with shells starfish horseshoe crabs
    With a sand base.
    I used flag on one side and resin on the other,,,, one looks clearer than the other ?
    I just did it 10 hr ago does it need to dry more as it is about 1/4″ thick ?
    I was told there the same with different carestices but the same outcome with clarity ?
    One is more yellow than the other.
    Thanking you
    Mike

    1. MAS Epoxies

      Hi Mike, Thank you for your question! There are a lot of environmental variables that could cause the clarity to be different, but you are correct that both resins should be equally clear. Give us a call to discuss your project at 800-755-8568.
      Sincerely,
      The MAS Epoxies Team

  2. Ice use Mas on a few other projects and like it.
    What product can i use on EPS foam

    1. MAS Epoxies

      Great Question!
      If you’re looking to have results that are clear, where a white EPS foam blank can be seen, we would recommend our 2:1 Non-blushing System for it’s clarity and strength. Epoxy products will not eat away at EPS foam like polyester resin products will so they are a great choice when working with EPS. We hope this helps. Feel free to contact us if you have further questions about your particular project.
      Sincerely,
      The MAS Epoxies Team

  3. Mick Beasley

    Is there a casting resin for thick pours up to an inch and a half thick? I am making a rolling pin.

    1. MAS Epoxies

      Hi Mick! I would try Deep Pour for that thickness.

  4. Hi can you mix lv and flag? Can you use flag as a base for clear coating and lv on top? Or would lv saturate better into raw unfinished wooden gunwales and flag on top??
    Thank You…
    Bill

    1. Hi Bill,

      Great question! First, yes you can mix LV and FLAG during process or after cured. If you’d like a custom viscosity feel free to mix them together and keep the 2:1 mix ratio by volume with your choice of hardener. After cured, epoxy products are generally compatible. Best to sand scuff and clean the surface between layers. Based on your brief description, yes LV would penetrate better into the wood and FLAG is great for clear coating so you’re on the right track. We also have our Penetrating Epoxy Sealer, which is designed to penetrate that you can use first, then coat with FLAG. That being said, if you have questions give our technical team a call. We’d be happy to walk through the process and any other questions.

      Sincerely,

      The MAS Epoxies Team

  5. Steve Ryan

    I have a de-laminated RV wall that is still wet. Can your product be used for this purpose? I have seen many videos where epoxy resins have been used for this purpose. Any info would be appreciated.

    1. MAS Epoxies

      Hi Steve! Great question. When applying epoxy to wet surfaces you can get foaming or bubbles that are not cosmetically appealing. If the cosmetics are less important than the structure than epoxy is a good choice, dry materials are always preferable to wet materials. Each project is unique and if you’d like to discuss your project further give us a call!

  6. Dana Thompson

    What would I use with epoxy resin silicone molds for ashtrays, bookmarks, pen, worded signs, etc.

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